1. Field of the Invention
The present invention relates to a semiconductor light-emitting device for irradiating with ultraviolet rays.
2. Description of Related Art
Nitride semiconductors, typified by GaN, AlN, InN, and mixed crystals thereof, are direct-transition semiconductor materials. Nitride semiconductors have the characteristic of having greater band gap energy than AlGaInAs-based semiconductors or AlGaInP-based semiconductors. Therefore, these nitride semiconductors are being focused on as materials constituting semiconductor laser elements for emitting light in the ultraviolet region, LED elements for emitting light in the ultraviolet region or the deep ultraviolet region (a wavelength range of approximately 320 nm to approximately 200 nm), and other semiconductor light-emitting elements.
Light in the ultraviolet region or deep ultraviolet region having a wavelength of 260 to 280 nm (may hereinafter be called ultraviolet light) is known to be efficient in disinfecting water. In addition, ultraviolet light is also known to be effective in water purification, disinfecting, high-speed decomposition treatment of pollutants, the medical field, and the like. Devices that utilize ultraviolet light can be made smaller and made to consume less power by employing semiconductor light-emitting devices that utilize semiconductor light-emitting elements for emitting light in the ultraviolet to deep ultraviolet region such as those described above.
A semiconductor light-emitting device for outputting light in the visible light region is packaged inexpensively by a mold with a resin whose light-radiating characteristics are easily controlled. However, ultraviolet light is absorbed by the resin used in the resin mold and the light cannot be extracted efficiently. The resin is deteriorated by the strong energy of ultraviolet light, causing a problem of stronger light absorption. Therefore, it is difficult to use a resin mold to package a semiconductor light-emitting device that emits light in the ultraviolet region.
Therefore, a package known as a CAN is utilized in a semiconductor light-emitting device that emits light in the ultraviolet region. FIG. 11 is a drawing of a package of a conventional semiconductor light-emitting device. The semiconductor light-emitting device D comprises an LED element 91, wires 95 for supplying electric power to the LED element 91, a reflective cup 93 fulfilling the role of a reflective plate for guiding light output from the LED element 91 upward, external pins 94 for supplying electric power, and a cap part 96 known as a CAN, as shown in FIG. 11. Furthermore, a translucent cover 97 for extracting light is adhered to the cap part 96 (see Japanese Laid-open Patent Application Nos. 2007-311707, 2008-258617, and others).
Light in the regions ultraviolet to deep ultraviolet have much energy and can adversely affect the human body in the eyes, skin, and the like. Therefore, it is necessary to recognize that ultraviolet light is being outputted by the semiconductor light-emitting device. When it is not possible to assess what range is being irradiated by the ultraviolet light (*1), problems with safety occur also when the device is actually used. The user must be able to immediately assess whether light is being emitted or not emitted, the extent of the light emission strength, and the range in which light is radiated.
Light in the regions ultraviolet to deep ultraviolet (approximately 320 nm to approximately 200 nm) cannot be perceived by the human eye, and in a semiconductor light-emitting device that emits light in the ultraviolet region, whether or not light is being emitted cannot be confirmed by the naked eye. Therefore, the light-emitting state of a semiconductor light-emitting device that emits light in the regions ultraviolet to deep ultraviolet can be confirmed utilizing a detector capable of detecting ultraviolet light, but it is troublesome to use a detector for this confirmation. When the device is utilized in common sanitary appliances or medical appliances, the common user is not likely to possess a detector and it is not easy to confirm the output of ultraviolet light.
In view of this, the ultraviolet-light-emitting device of Japanese Laid-open Patent Application No. 2009-177098 comprises an ultraviolet light LED chip from which ultraviolet light is outputted and a light-receiving element for detecting ultraviolet light. It is possible to monitor whether or not the ultraviolet light LED chip is activated by providing a visible light LED chip for monitoring activation, and causing the chip to be activated and deactivated based on the output of the light-receiving element.
However, in the ultraviolet-light-emitting device disclosed in Japanese Laid-open Patent Application No. 2009-177098, although it is possible to detect ultraviolet light without using equipment, a light-receiving element or a monitoring visible light LED chip attached to the package are needed. Because of this, the ultraviolet-light-emitting device disclosed in Japanese Laid-open Patent Application No. 2009-177098 has numerous configurationally members, and it is difficult to reduce this device in size and cost.
There are also cases in which the ultraviolet-light-emitting device is disposed inside another device, in which case it is sometimes difficult or even impossible to ascertain the starting light LED chip for monitoring, and it is sometimes difficult to accurately confirm whether or not the ultraviolet-light-emitting device has activated.